J.D. Dana on Volcanic action at Mauna Loa. 241 
Itis only four hours walk from us, and it might be reached in 
two hours, were the route direct and the road good. The rate 
of progress now is about one mile a week. It may come faster 
when it gets through the forest. Probably six or eight weeks 
will decide the question whether Hilo shall remain in its ver- 
dant robes or be swept with a besom of fire. 
Arr, XXVIU.—On Volcanic action at Mauna Loa; by James 
D. Dana. ’ 
Te recent eruption of Mauna Loa, so vividly described by 
the Rev. Mr. Coan of Hilo, sustains fully the conclusions of the 
writer in his Expl. Exp., Geological Report; and as those con- 
clusions are, in part at least, at variance with preconceived no- 
tions, a.review of them will not be out of place. It will prob- 
ably require many reiterations of the facts, before so magnificent 
an attendant upon volcanoes as earthquakes shall be allowed to 
have only an incidental place among the phenomena, 
The main conclusions to which I refer, are briefly as follows — 
1. The quietness of the eruption.—According to Mr. Coan, the 
lava has reached in its windings a distance of 65 miles: yet it 
broke out without an earthquake ; as in the eruption of 1852 and 
1846, a light on the mountains was the first announcement. The 
Progress also has been as quiet as the commencement. 
2. The eruption through opened fissures.—T he craters at sum- 
mit did not overflow; the mountain was broken through at a 
height of 12,000 feet—and the fissure or fissures continued down 
the mountain, the lavas flowing in the fissure at a rapid rate—as 
they should, with a head, more than 12,000 feet above the sea; 
—in some places overflowing, and spreading widely, and in 
— confined to the fissure. 
Must be a fissure opening from below upward, or several fissures 
along a common sre dg and -the fissure or fissures may ex- 
tend so as to reach the surface only:at intervals, so that the out- 
breaks shall be more or less interrupted. Thus it has espn or 
the modern eruptions of Mauna Loa .and Kilauea. The idea o 
a shaft being suddenly struck through, so as to become the con- 
duit of a:side ctater, and ;this crater the sonrce of Java.of the 
a 
®tuption, is wholly-opposed by the facts.on Hawaii, as; 
Sconp Szems, Vol. XXI, No. 62.—March, 1856. 31 
